Portable display devices such as foldable and flexible display devices have become a focus of research and development in display technology in recent years. A flexible display device is a bendable or deformable display device having a flexible display panel. Examples of flexible display devices include a flexible organic light emitting display (OLED) device, a flexible electrophoretic display (EPD) device, and a flexible liquid crystal display (LCD) device. As a new generation display device, the flexible display device is thinner and tighter, having high contrast, high responsiveness, and high brightness. It also provides full color and a wide viewing angle. The flexible display device has found a wide range of applications in mobiles phones, personal digital assistance (PDAs), digital cameras, on-board displays, notebook computers, on-wall televisions, as well as various military applications. A flexible display device includes a flexible array substrate. A base substrate of the flexible array substrate can be made of flexible material such as plastic.